The SKS trigger group is one of those times where I tell people only one thing.
If you don't know what you are doing, if you aren't intimately familiar with how an SKS trigger group works, then DON'T MESS WITH IT!
Creating a potential "negative engagement" with your trigger is bad news.
See here for more info on "positive", "neutral", and "negative" engagement.
This video
http://www.americangunsmith.com/view.php?id=69 is very good but the guy presenting is terrible in front of the camera so sometimes he jumps around a bit.
Oh and if you do decide to give it a try... disassembly of the trigger group requires punch pins, a good rubber mallet, and a vice mounted on a bench that won't move.
I'm not kidding, it really does.